Question

I have a custom View Engine that derives from WebFormViewEngine. There’s a lot of stuff going on in here, mostly caching. I want to be able to use WebFormViewEngine AND RazorViewEngine at the same time, is this possible? Ideally I’d like to do;

ViewEngines.Add(new MyViewEngine<WebFormsViewEngine>());
ViewEngines.Add(new MyViewEngine<RazorViewEngine>());

if a .ascx/.aspx/.master file exists then use WebForms, otherwise use Razor is a .cshtml file exists.

EDIT: I should of worded my question better. As my custom view engine derives from WebFormViewEngine it obviously uses WebForms, I can’t derive from two classes. I can derive from RazorViewEngine but then I’ll loose WebForms. I can duplicate my code entirely, derive from RazorViewEngine and edit the views file extensions, etc. but as I said I’ve got a lot of custom code in my view engine and would be duplicating hundreds of lines.

WebFormViewEngine and RazorViewEngine derive from BuildManagerViewEngine which in turn implements IViewEngine. The problem with that is I have to implement methods CreatePartialView() and CreateView() but how would I know what to return (WebForms/Razor?) using generics?

Answer 1

In the end I ended up with creating an abstract class: public abstract class MyViewEngine : BuildManagerViewEngine, IViewEngine { } and then implement/override the FindView and FindPartialView methods (which had my caching code in). I had an abstract method public abstract void SetSearchPaths(); that was called in my ctor.

I then created another class that derived from MyViewEngine for WebForms specifically:

public class MyViewEngineWebForms : MyViewEngine
{
    public override void SetSearchPaths()
    {
        base.MasterLocationFormats = new string[] { "~/Skins/{2}/Views/{1}/{0}.master", "~/Skins/{2}/Views/Shared/{0}.master" };
        base.ViewLocationFormats = new string[] { "~/Skins/{2}/Views/{1}/{0}.aspx", "~/Skins/{2}/Views/Shared/{0}.aspx", "~/Skins/Shared/Views/{0}.aspx" };
        base.PartialViewLocationFormats = new string[] { "~/Skins/{2}/Views/{1}/{0}.ascx", "~/Skins/{2}/Views/Shared/{0}.ascx", "~/Skins/Shared/PartialViews/{0}.ascx" };
        base.FileExtensions = new string[] { "aspx", "ascx", "master" };
    }

    protected override IView CreatePartialView(ControllerContext controllerContext, string partialPath)
    {
        return new WebFormView(controllerContext, partialPath, null, base.ViewPageActivator);
    }

    protected override IView CreateView(ControllerContext controllerContext, string viewPath, string masterPath)
    {
        return new WebFormView(controllerContext, viewPath, masterPath, base.ViewPageActivator);
    }
}

and did exactly the same for Razor but change the file extensions to .cshtml/.vbhtml and change WebFormView to RazorView. Add them to the ViewEngine collection:

ViewEngines.Engines.Clear();
ViewEngines.Engines.Add(new SeeTicketsWebFormsViewEngine());
ViewEngines.Engines.Add(new SeeTicketsRazorViewEngine());

and now they work perfectly again, side by side with all of my custom caching logic.